(a) Field of the Invention
This invention relates to prepackaged, disposable hypodermic syringes having a double-ended hypodermic needle, for use in combination with medicament containing cartridge ampoules, which are provided with means to prevent accidental engagement between the hypodermic needle and the cartridge ampoule and consequent premature discharge of the ampoule contents prior to intended use of the syringes.
(b) Description of the Prior Art
It is known in prepackaged hypodermic syringes, for example as illustrated by Keller U.S. Pat. No. 3,375,825, to use a hypodermic needle sheath to serve a second function as a plunger rod. It is also known, for example as described by Maki U.S. Pat. No. 3,150,661, to use an annular projection or ridge around the inside perimeter of a hypodermic needle hub unit to lock into a mating annular groove around the outside perimeter of a crimped-on metal overcap of a cartridge ampoule in order to maintain the inner end of a double ended hypodermic needle affixed to the needle hub out of piercing engagement with the diaphragm closing the inner end of the cartridge ampoule.
However, it is not believed known in the prior art to employ the concept involved in the present invention for preventing accidental piercing of the cartridge ampoule diaphragm by the inner end of a double-ended hypodermic syringe needle comprising either (a) reversing the cartridge ampoule within the barrel of the syringe holder and further providing the latter with means for restraining movement of the ampoule within the syringe barrel or (b) providing such restraint means within the syringe barrel with the cartridge ampoule is properly oriented within the syringe barrel for use.